(a) Field of the Invention
The present invention relates to an upshift control system and method of an automatic transmission that control hydraulic pressure of an on-coming element based on a change of vehicle speed during upshift.
(b) Description of the Related Art
An automatic transmission changes gears based on inputs such as vehicle speed and throttle opening. During shifting, an off-going element is released and an on-coming element is engaged by controlling hydraulic pressure supplied to the elements. The hydraulic pressure is controlled by solenoid valves.
Generally, hydraulic pressure of the off-going element is reduced while hydraulic pressure of the on-coming element is increased enough to endure the new speed ratio. This method uses a one-way clutch. However, since torque generated by change of engine inertia is reduced during shifting, shift shock may occur.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.